#define _BSD_SOURCE
#ifdef _GNU_SOURCE
#define HAD_SOURCE
#undef _GNU_SOURCE
#endif
#include <glob.h>
#ifdef HAD_SOURCE
#undef HAD_SOURCE
#define _GNU_SOURCE
#endif
#include <fnmatch.h>
#include <sys/stat.h>
#include <dirent.h>
#include <limits.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <stddef.h>
#include <unistd.h>
#include <pwd.h>

struct match
{
    struct match *next;
    char name[];
};

static int append(struct match **tail, const char *name, size_t len, int mark)
{
    struct match *new = malloc(sizeof(struct match) + len + 2);
    if (!new) return -1;
    (*tail)->next = new;
    new->next = NULL;
    memcpy(new->name, name, len+1);
    if (mark && len && name[len-1]!='/') {
        new->name[len] = '/';
        new->name[len+1] = 0;
    }
    *tail = new;
    return 0;
}

static int do_glob(char *buf, size_t pos, int type, char *pat, int flags, int (*errfunc)(const char *path, int err), struct match **tail)
{
    /* If GLOB_MARK is unused, we don't care about type. */
    if (!type && !(flags & GLOB_MARK)) type = DT_REG;

    /* Special-case the remaining pattern being all slashes, in
     * which case we can use caller-passed type if it's a dir. */
    if (*pat && type!=DT_DIR) type = 0;
    while (pos+1 < PATH_MAX && *pat=='/') buf[pos++] = *pat++;

    /* Consume maximal [escaped-]literal prefix of pattern, copying
     * and un-escaping it to the running buffer as we go. */
    ptrdiff_t i=0, j=0;
    int in_bracket = 0, overflow = 0;
    for (; pat[i]!='*' && pat[i]!='?' && (!in_bracket || pat[i]!=']'); i++) {
        if (!pat[i]) {
            if (overflow) return 0;
            pat += i;
            pos += j;
            i = j = 0;
            break;
        } else if (pat[i] == '[') {
            in_bracket = 1;
        } else if (pat[i] == '\\' && !(flags & GLOB_NOESCAPE)) {
            /* Backslashes inside a bracket are (at least by
             * our interpretation) non-special, so if next
             * char is ']' we have a complete expression. */
            if (in_bracket && pat[i+1]==']') break;
            /* Unpaired final backslash never matches. */
            if (!pat[i+1]) return 0;
            i++;
        }
        if (pat[i] == '/') {
            if (overflow) return 0;
            in_bracket = 0;
            pat += i+1;
            i = -1;
            pos += j+1;
            j = -1;
        }
        /* Only store a character if it fits in the buffer, but if
         * a potential bracket expression is open, the overflow
         * must be remembered and handled later only if the bracket
         * is unterminated (and thereby a literal), so as not to
         * disallow long bracket expressions with short matches. */
        if (pos+(j+1) < PATH_MAX) {
            buf[pos+j++] = pat[i];
        } else if (in_bracket) {
            overflow = 1;
        } else {
            return 0;
        }
        /* If we consume any new components, the caller-passed type
         * or dummy type from above is no longer valid. */
        type = 0;
    }
    buf[pos] = 0;
    if (!*pat) {
        /* If we consumed any components above, or if GLOB_MARK is
         * requested and we don't yet know if the match is a dir,
         * we must confirm the file exists and/or determine its type.
         *
         * If marking dirs, symlink type is inconclusive; we need the
         * type for the symlink target, and therefore must try stat
         * first unless type is known not to be a symlink. Otherwise,
         * or if that fails, use lstat for determining existence to
         * avoid false negatives in the case of broken symlinks. */
        struct stat st;
        if ((flags & GLOB_MARK) && (!type||type==DT_LNK) && !stat(buf, &st)) {
            if (S_ISDIR(st.st_mode)) type = DT_DIR;
            else type = DT_REG;
        }
        if (!type && lstat(buf, &st)) {
            if (errno!=ENOENT && (errfunc(buf, errno) || (flags & GLOB_ERR)))
                return GLOB_ABORTED;
            return 0;
        }
        if (append(tail, buf, pos, (flags & GLOB_MARK) && type==DT_DIR))
            return GLOB_NOSPACE;
        return 0;
    }
    char *p2 = strchr(pat, '/'), saved_sep = '/';
    /* Check if the '/' was escaped and, if so, remove the escape char
     * so that it will not be unpaired when passed to fnmatch. */
    if (p2 && !(flags & GLOB_NOESCAPE)) {
        char *p;
        for (p=p2; p>pat && p[-1]=='\\'; p--);
        if ((p2-p)%2) {
            p2--;
            saved_sep = '\\';
        }
    }
    DIR *dir = opendir(pos ? buf : ".");
    if (!dir) {
        if (errfunc(buf, errno) || (flags & GLOB_ERR))
            return GLOB_ABORTED;
        return 0;
    }
    int old_errno = errno;
    struct dirent *de;
    while (errno=0, de=readdir(dir)) {
        /* Quickly skip non-directories when there's pattern left. */
        if (p2 && de->d_type && de->d_type!=DT_DIR && de->d_type!=DT_LNK)
            continue;

        size_t l = strlen(de->d_name);
        if (l >= PATH_MAX-pos) continue;

        if (p2) *p2 = 0;

        int fnm_flags= ((flags & GLOB_NOESCAPE) ? FNM_NOESCAPE : 0)
            | ((!(flags & GLOB_PERIOD)) ? FNM_PERIOD : 0);

        if (fnmatch(pat, de->d_name, fnm_flags))
            continue;

        /* With GLOB_PERIOD, don't allow matching . or .. unless
         * fnmatch would match them with FNM_PERIOD rules in effect. */
        if (p2 && (flags & GLOB_PERIOD) && de->d_name[0]=='.'
            && (!de->d_name[1] || de->d_name[1]=='.' && !de->d_name[2])
            && fnmatch(pat, de->d_name, fnm_flags | FNM_PERIOD))
            continue;

        memcpy(buf+pos, de->d_name, l+1);
        if (p2) *p2 = saved_sep;
        int r = do_glob(buf, pos+l, de->d_type, p2 ? p2 : "", flags, errfunc, tail);
        if (r) {
            closedir(dir);
            return r;
        }
    }
    int readerr = errno;
    if (p2) *p2 = saved_sep;
    closedir(dir);
    if (readerr && (errfunc(buf, errno) || (flags & GLOB_ERR)))
        return GLOB_ABORTED;
    errno = old_errno;
    return 0;
}

static int ignore_err(const char *path, int err)
{
    return 0;
}

static void freelist(struct match *head)
{
    struct match *match, *next;
    for (match=head->next; match; match=next) {
        next = match->next;
        free(match);
    }
}

static int sort(const void *a, const void *b)
{
    return strcmp(*(const char **)a, *(const char **)b);
}

static int expand_tilde(char **pat, char *buf, size_t *pos)
{
    char *p = *pat + 1;
    size_t i = 0;

    char delim, *name_end = __strchrnul(p, '/');
    if ((delim = *name_end)) *name_end++ = 0;
    *pat = name_end;

    char *home = *p ? NULL : getenv("HOME");
    if (!home) {
        struct passwd pw, *res;
        switch (*p ? getpwnam_r(p, &pw, buf, PATH_MAX, &res)
               : getpwuid_r(getuid(), &pw, buf, PATH_MAX, &res)) {
        case ENOMEM:
            return GLOB_NOSPACE;
        case 0:
            if (!res)
        default:
                return GLOB_NOMATCH;
        }
        home = pw.pw_dir;
    }
    while (i < PATH_MAX - 2 && *home)
        buf[i++] = *home++;
    if (*home)
        return GLOB_NOMATCH;
    if ((buf[i] = delim))
        buf[++i] = 0;
    *pos = i;
    return 0;
}

int glob(const char *restrict pat, int flags, int (*errfunc)(const char *path, int err), glob_t *restrict g)
{
    struct match head = { .next = NULL }, *tail = &head;
    size_t cnt, i;
    size_t offs = (flags & GLOB_DOOFFS) ? g->gl_offs : 0;
    int error = 0;
    char buf[PATH_MAX];
    
    if (!errfunc) errfunc = ignore_err;

    if (!(flags & GLOB_APPEND)) {
        g->gl_offs = offs;
        g->gl_pathc = 0;
        g->gl_pathv = NULL;
    }

    if (*pat) {
        char *p = strdup(pat);
        if (!p) return GLOB_NOSPACE;
        buf[0] = 0;
        size_t pos = 0;
        char *s = p;
        if ((flags & (GLOB_TILDE | GLOB_TILDE_CHECK)) && *p == '~')
            error = expand_tilde(&s, buf, &pos);
        if (!error)
            error = do_glob(buf, pos, 0, s, flags, errfunc, &tail);
        free(p);
    }

    if (error == GLOB_NOSPACE) {
        freelist(&head);
        return error;
    }
    
    for (cnt=0, tail=head.next; tail; tail=tail->next, cnt++);
    if (!cnt) {
        if (flags & GLOB_NOCHECK) {
            tail = &head;
            if (append(&tail, pat, strlen(pat), 0))
                return GLOB_NOSPACE;
            cnt++;
        } else
            return GLOB_NOMATCH;
    }

    if (flags & GLOB_APPEND) {
        char **pathv = realloc(g->gl_pathv, (offs + g->gl_pathc + cnt + 1) * sizeof(char *));
        if (!pathv) {
            freelist(&head);
            return GLOB_NOSPACE;
        }
        g->gl_pathv = pathv;
        offs += g->gl_pathc;
    } else {
        g->gl_pathv = malloc((offs + cnt + 1) * sizeof(char *));
        if (!g->gl_pathv) {
            freelist(&head);
            return GLOB_NOSPACE;
        }
        for (i=0; i<offs; i++)
            g->gl_pathv[i] = NULL;
    }
    for (i=0, tail=head.next; i<cnt; tail=tail->next, i++)
        g->gl_pathv[offs + i] = tail->name;
    g->gl_pathv[offs + i] = NULL;
    g->gl_pathc += cnt;

    if (!(flags & GLOB_NOSORT))
        qsort(g->gl_pathv+offs, cnt, sizeof(char *), sort);
    
    return error;
}

void globfree(glob_t *g)
{
    size_t i;
    for (i=0; i<g->gl_pathc; i++)
        free(g->gl_pathv[g->gl_offs + i] - offsetof(struct match, name));
    free(g->gl_pathv);
    g->gl_pathc = 0;
    g->gl_pathv = NULL;
}

weak_alias(glob, glob64);
weak_alias(globfree, globfree64);
